1. Field of the Invention
This invention relates to a compression hip screw system and, more particularly, to an improved self-compressing hip lag screw with mechanisms to retain the compression screw fixed with respect to the barrel/side plate and with the lag screw and compression screw coupled so as to preclude lateral movement of the compression screw into the hip muscle while still allowing normal bone impaction and lag screw collapse/movement laterally.
2. Description of the Background Art
The hip joint is the most heavily stressed load carrying bone joint of the human body. It is essentially a ball and socket joint formed by the top of the femur which pivots within the up-shaped acetabulum at the base of the pelvis. When a break or fracture occurs adjacent to the top of the femur, the separated portions of the femur must be held together while healing occurs.
Various mechanisms for holding bone portions together during healing are in commercial use today while others are disclosed in the patient literature. The most common devices are compression hip screws of one design or another. Such devices may utilize as lag screw extended through an aperture bored through the upper part of the femur and its broken fragment to hold the fragment in proper position with respect to the majority of the femur during healing. A side plate is screwed to the femur. The side plate has a barrel at its upper end for receiving the lag screw. A compression screw secures the lag screw to the side plate. Devices of this nature are disclosed in U.S. Pat. No. 2,397,545 to Harding; 4,621,629to Koeneman; 4,628,923 to Medoff; 4,432,358 to Fixel; and 4,438,762 to Kyle.
All of the known prior art, whether in the patent literature as disclosed above, or in commercial devices, fails to take into account the shifting of the lag screw and its compression screw in the barrel as the break heals and the fragments move closer together. When this movement occurs, the head of the compression screw moves laterally away from the break and into the soft tissue causing discomfort, pain and a painful bursa.
As illustrated by the background art, efforts are continuously being made in an attempt to improve compression hip screw systems. No prior effort, however, provides the benefits attendant with the present invention. Additionally, the prior patents and commercial techniques do not suggest the present inventive combination of component elements arranged and configured as disclosed and claimed herein.
The present invention achieves its intended purposes, objects, and advantages through a new, useful and unobvious combination of component elements, with the use of a minimum number of functioning parts, at a reasonable cost to manufacture, and by employing only readily available materials.
Therefore, it is an object of this invention to provide an improved compression hip screw system comprising a lag screw having a first end with external threads insertable into the proximal end of a femur head and broken fragments thereof and having a second end with an axial bore; a barrel/side plate having a plate-like member attachable at its distal end to a femur and having a barrel at its proximal end for receiving the second end of the lag screw; a compression screw within the barrel and extending into the bore of the lag screw; a supplemental set screw threaded through the barrel/side plate to secure the compression screw in a fixed position with respect to the barrel/side plate; and coupling means joining the lag screw and compression screw to allow a telescoping motion between the lag screw and the compression screw in the event of axial movement of the broken fragment and lag screw with respect to the proximal end of the femur and the barrel/side plate.
It is a further object of the present invention to preclude movement of a compression screw away from a bone being healed.
It is a further object of this invention to take up the movement of a intertrocanteric fracture during healing through the intercoupling of a lag screw and a barrel/side plate.
The foregoing has outlined some of the more pertinent objects of this invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the present invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.